With a loud sputtering roar, something like Terry Mapes' own feelings at that moment, Skybird, her little blue-and-gold airplane sprang forward and taxied over the flying field, taking the air gracefully as a leaping horse, under the guidance of its youthful pilot. Terry Mapes was working off steam. Half angry, half frightened, the girl knew that a flight in her plane was the quickest way to get hold of her nerves and make her head clear for thinking what was to be done. -Those boys - she muttered between close-pressed lips. -What's happened to them now? Starting out for a flight to Paris and...